1. Field of the Invention
The e invention pertains to the forming of air flow control orifices in a film or web by the use of a multiple faceted sharp punch wherein the punch forms a plurality of flexible valve flaps which define the orifice.
2. Description of the Related Art
Post-surgery medical patients often experience body temperature fluctuations, and a treatment for such conditions includes covering the patient's body with a thermal blanket. The thermal blanket may be inflated with a warm pressurized air, and orifices formed in the blanket side disposed toward the patient permit the warm air to be discharged from the blanket envelope upon the patient. Such a single use patient warming blanket is shown in the assignee's U.S. Pat. No. 5,125,238.
As will be appreciated from the above identified patent, the lower side of the blanket disposed toward the patient is provided with a plurality of orifices through which the warm air flows toward the patient. Preferably, the blanket lower side outer surface is provided with a non-woven, fibrous layer which, though thin, is sufficient to increase the frictional characteristics of the blanket envelope forming material, which is usually a thin plastic film of a flexible nature.
Usually, the warming blanket is directly placed upon the patient's body wherein the lower blanket surf ace, i.e. the non-woven material, will directly engage the patient's body. As disclosed in the assignee's above identified patent, the blanket is formed of a plurality of cells by heat sealing the blanket envelope upper and lower films at spaced locations resulting in a blanket form having a plurality of projections or protrusions intermediate recesses or depressions located adjacent the film welded or staked points.
The air control orifices formed in the blanket lower film and non-woven material are usually evenly spaced over the lower surface of the blanket, and some of the orifices will be defined at the lowermost regions of the bulbous projections which directly engage the patient's body. Accordingly, air flowing from such orifices in direct engagement with the patient's body will tend to impose a higher temperature air upon the patient's body than the air discharged from the orifices formed in the blanket recesses which are spaced from the patient's body permitting the air to be diffused, cooled and distributed prior to engaging the patient's body.
Heretofore, the orifices of a patient warming blanket have not been capable of automatically sensing the presence of the patient's body and preventing direct exposure of the air released from the blanket.